1. Field of the Invention
The present invention relates to a message decoding method and an electronic system thereof, and more particularly to a message decoding method and an electronic system thereof which uses a character-based switching technique and a buffer which uses a point accumulation technique.
2. Description of the Related Art
High Definition radio (HD radio) has been developed for several years and can be broadcast through the existing FM or AM radio channels. HD radio is different from the traditional FM and AM in that it is able to provide a high definition sound quality as well as a program service.
However, the message decoding algorithm used by the Digital Signal Processor (DSP) of the receiver for processing the HD radio received from the Radio Broadcast Data System (RBDS) produces considerable errors and causes the users to receive error text messages. The main cause of these erroneous messages is due to the low sampling rate of the DSP.
FIG. 1 is a table showing the decoded characters produced by a DSP with the relative position and time.
Take a word group of eight characters as an example. At each sampling, the DSP can only decode two characters with a corresponding position; the string will be updated and the word group will be shown on the display. For instance, assume that the broadcast system sends out two groups of words, which are ABCDEFGH and 12345678, respectively. As shown in FIG. 1, the first word group is received at time t1, with the first two characters decoded in the first position; then the first two characters appear on the display as D1=“ABΔΔΔΔΔΔ” (Δ representing a blank space). At time t2, the DSP decodes another two characters of the first word group at position three; then the first word group appears on the display as D2=“ABΔΔEFΔΔ”. Due to the sampling rate of the DSP, a word group may be displayed before it is fully decoded; thus the word group shown on the display may be incomplete.
Next, the DSP decodes the characters at position two and position four at time t3 and t4, respectively. Then the display D4=“ABCDEFGH” is the correct representation of the first word group transmitted by the broadcast system.
Next, the broadcast system sends out a second word group at t5, and the DSP decodes two characters at position two. However, there are no means to determine that these decoded characters are obtained from the second word group, which needs to be separated from the first word group; as a result, the characters previously obtained are replaced by the latest decoded characters at the corresponding position, and then the word group is shown directly on the display. Therefore, the display shows D3=“AB34EFGH”, which intermingles the first word group with the second word group and causes the user to receive an erroneous message.
In the prior art, this problem may be resolved by improving the hardware or the software. Hardware improvement can be done by enhancing the speed of the DSP to increase the sampling rate so that the characters of the word group can be completely obtained before it is displayed through a simple software algorithm. However, high speed DSP is expensive and consumes a considerable amount of electricity when placed into an embedded system and therefore is not a feasible solution.
On the other hand, software improvement can be done by comparing the word group whenever the word group is updated. This can be used to check for the consistency of the word group, and it can be used to identify whether the word group has been completely received, or whether a new message has been sent by the broadcast system. As a result, this may prevent intermingling of the word groups and improve the probability of displaying correct messages.
The present invention provides a method for decoding a message directed to improve the accuracy of a message decoding service.